Why Can't Women Sleep?

Editor's Note: This article is excerpted from the spring 2008 issue of Ms. Magazine, available on newsstands now.

Can't sleep? Well you're not alone, especially among women.

A 2007 poll by the National Sleep Foundation found that 67 percent of women frequently experience sleep problems and 29 percent use some type of sleep aid at least a few nights a week. Other surveys have consistently found that nearly half again as many women as men complain of insomnia.

Yet 75 percent of sleep research has been done on men, and until recently the researchers have been primarily men. The major texts for sleep studies have had, until recently, little to say about women's sleep.

As with other conditions that affect more women than men and are not well understood, there's a tendency to assume that the problem is psychological. When 501 physicians were interviewed about how they treated insomnia, they revealed that they asked an average of just two and a half questions, mostly about psychological problems. And since doctors believe it's all in the head, there's little impetus to research insomnia. In 2005, the National Institutes of Health spent less than $20 million on the condition, although it affects as many as a third of the U.S. adult population. Most of those funds were directed toward treating and managing the problem, while less than $4 million went to investigations of neurophysiological and neuroendocrinal mechanisms -- the kind of basic research that might lead to an understanding of cause.

There's no question that stress can lead to insomnia, and that women are under stress. Juggling the demands of work, marriage and motherhood, they often don't have time to sleep, and when they do they're so revved up that they've forgotten how. Women are also conditioned to internalize conflicts rather than act them out. And they're statistically more likely to be poor, to be trapped in conditions over which they have little control, and to be subject to abuse and violence. But to overestimate the effects of social and psychological factors is to miss the crucial connections between female physiology and sleep.

Before puberty, girls do not sleep worse than boys. At adolescence, though, girls become approximately two and a half times more likely than boys to have insomnia, according to a 2006 study published in the Journal Pediatrics. Adolescence is when young women have to deal with confusing cultural messages about being "girls," but it's also that time when surges of estrogen and progesterone make sleep more vulnerable. Estrogen increases the secretion of cortisol, promoting a stress response that's both stronger and longer in women than in men. Women have been found to have longer-lasting cortisol responses during the phases of the menstrual cycle when estrogen and progesterone levels are highest.

As we're exposed to monthly dips and surges in estrogen and progesterone throughout our reproductive years, the stress system stays primed for hyperreactivity, which gives us greater vulnerability to stress-related disorders. Men have higher rates of alcoholism, addiction, autism and schizophrenia, but women are more prone to panic disorder, generalized anxiety disorder, post-traumatic stress disorder and depression. Such differences arise during puberty, continue through the childbearing years and decline after menopause to a rate same age.

Menopause is another trouble spot for sleep; at this point, women's sleep complaints more than double. The physiological explanations given for this are hot flashes and apnea -- a breathing disorder that becomes more frequent in women after menopause, partly because weight gain makes the breathing passages smaller and partly because progesterone, which has a protective effect on breathing, declines. But the explanation usually given for menopausal insomnia is midlife depression about aging, empty nests, divorce or loss of parents.